1. Field of the Invention
The present invention relates to a process for filling a powder, process which is effective in manufacturing sintered members, composite materials, green compacts, preliminarily sintered members (or preforms), and so forth, and an apparatus therefor. Moreover, it relates to a process for producing a composite material, process which uses the process or the apparatus.
2. Description of the Related Art
Regardless of the types of powdery material such as metallic powder, ceramic powder and the like, there are a variety of processes for producing green compacts, and so on. For instance, metallic sintered bodies are produced by way of a process comprising steps, such as filling a metallic powder into a mold, molding the metallic powder by pressurizing, sintering the metallic powder, etc. When compact magnetic cores, and so forth, are produced, sintering the metallic powder is not carried out, but filling a metallic powder as well as molding the metallic powder by pressurizing are carried out. In the case of molded bodies of ceramic, filling a ceramic powder, molding the ceramic powders together with a binder, and so forth, and further calcining the ceramic powder are carried out. Depending on the types of products, there are a great variety of processes for producing such green compacts, and so on. However, the step of filling a powder in a cavity is usually carried out in all of the cases.
In the meantime, depending on how the filling step is carried out, there is a fear of varying the dimensions, densities, and so forth, of molded bodies, sintered bodies, and the like. Hence, in order to attain the dimensional stability, high densification, and so on, a variety of measures have been developed so that the filling ability can be enhanced in the filling step.
For example, Japanese Unexamined Patent Publication (KOKAI) No. 7-207,303 and Japanese Unexamined Patent Publication (KOKAI) No. 10-180,492 disclose processes in which a vibration is applied to a powder which is put in a cavity. Moreover, Japanese Unexamined Patent Publication (KOKAI) No. 10-296,498 and Japanese Unexamined Patent Publication (KOKAI) No. 5-279,702 disclose processes in which a powder is divided into several portions and each portion is filled separately in a cavity.
However, even if it is possible to improve an apparent density of a powder by such processes, the resulting apparent density and uniformity have not necessarily arrived at sufficient levels. Hence, it has been desired to develop a filling process which makes it possible to furthermore improve the apparent density, and so forth.
The present invention has been developed in view of such circumstances. Namely, it is an object of the present invention to provide a process for filling a powder, process which can furthermore improve the filling ability of a powder, and an apparatus therefor.
Moreover, it is another object of the present invention to provide a process for producing a composite material, such as a process which uses the filling process or apparatus according to the present invention.
Note that, as illustrated in FIG. 4, Japanese Unexamined Patent Publication (KOKAI) No. 7-207,303, set forth above, discloses a process comprising the steps of filling a powder by putting a weight on a powder which is held in a container; and vibrating the container. However, the weight merely applies a load continuously to an upper layer portion of the powder which is held in the container. Specifically, the load which is applied to the powder is made uniform in the vertical direction so that it is simply intended to entirely improve the apparent density of the filled powder. Then, paragraphs [0008] and [0009] of the publication disclose that the filled volume of the powder is controlled by way of the weight by measuring the positions of the weight which sinks gradually in the container with a sensor. In view of the descriptions, it is not believed that the weight swings, for example, moves up and down in the vertical direction, and so forth, in the container. Therefore, it should be noted in advance that the process or apparatus which is disclosed in the publication differs completely from the present invention which will be described hereinafter with regard to the engineering concept and arrangement.
The inventors of the present invention have studied wholeheartedly in order to solve the aforementioned problems. As a result of trial and error over and over again, they thought of swinging a swinging body in a cavity in which a powder is held. Thus, they arrived at completing the present invention.
(Process for Filling Powder)
Namely, a process for filling a powder according to the present invention comprises the steps of: charging a powder into a cavity of a container; and, after the charging step, vibrating a swinging body on the powder which is held in the cavity, thereby filling the powder with a high density.
In accordance with the present powder filling process, in the vibrating step, the swinging body is swung actively in the cavity in which the powder is charged in the cavity. Here, the term, xe2x80x9cswinging,xe2x80x9d implies that at least a part of the swinging body (e.g., usually, a lower portion thereof) moves in the vertical direction, and the like, so that it is repeatedly put in a state that it is brought into contact with or is kept on contacting with a top surface or an upper layer portion of the powder and conversely in a state that it is separated therefrom to float thereover. In this regard, the present powder filling process is distinguished from the conventional process in which the weight is placed on the top surface of the powder so that the weight pressurizes the powder continuously. Thus, by the vibrating step, the present invention can improve the filling ability of the powder more than the conventional process does. Although the mechanism has not necessarily been cleared yet, it is believed as follows at present.
When the swinging body swings in the cavity in which the powder is held, discontinuous contacts take place between the swinging body and the powder (e.g., especially, the upper layer portion). When the swinging body is brought into contact with the powder, the swinging body gives vibrations, loads, and so forth, to the powder. On the other hand, when the swinging body floats, it is possible for the powder to move freely. The repetition of these operations promotes the movement of the powder. Accordingly, the constituent particles, or the like, move so as to engage with each other, and thereby occupy the positions where they mutually bury the respective spaces between them. Thus, it is believed that the constituent particles, or the like, transfer to such a filling state that they are furthermore densified. Note that the swinging direction of the swinging body is not limited to the vertical direction and accordingly the swinging body can swing in the horizontal direction or in the diagonal directions.
(Apparatus for Filling Powder)
The present invention is not limited to a process for filling a powder. For instance, it is possible to grasp the present invention as an apparatus for filling a powder, apparatus which can realize the present powder filling process.
Namely, it is possible to use the present invention to constitute an apparatus for filling a powder, apparatus which comprises: a container having a cavity into which a powder is charged; a swinging body disposed swingably in the cavity; and a vibrator for swinging the swinging body on the powder which is charged into the cavity.
(Process for Producing Composite Material)
Moreover, it is possible to grasp the present invention as a process for producing a composite material, process which uses the present powder filling process or the present powder filling apparatus.
Namely, the present invention can be a process for producing a composite material, wherein a reinforcement member is dispersed in a matrix metal, process which comprises the steps of: charging a powder of the reinforcement member into a cavity of a mold for casting; after the charging step, vibrating a swinging body on the powder which is held in the cavity, thereby filling the powder with a high density; and impregnating a molten metal of the matrix metal into the reinforcement member by pouring with pressure after the vibrating step.
In accordance with the present invention, it is possible to fill a powder with a high apparent density. For example, it is possible to readily produce a composite material in which a reinforcement member is dispersed in a matrix metal with a large filling ratio.